code: def test_unique(self, data, categories, expected_data, ordered):
      dtype = CategoricalDtype(categories, ordered=ordered)
  
      idx = CategoricalIndex(data, dtype=dtype)
      expected = CategoricalIndex(expected_data, dtype=dtype)
      tm.assert_index_equal(idx.unique(), expected)
  
imports: import numpy
  import pytest
  from pandas._config import using_pyarrow_string_dtype
  from pandas._libs import index
  from pandas._libs.arrays import NDArrayBacked
  import pandas
  from pandas import Categorical, CategoricalDtype
  import pandas._testing
  from pandas.core.indexes.api import CategoricalIndex, Index
label_desc: Use image node_id 9 for calling the TestCategoricalIndex obj's underlying member method code with example usage: obj.test_unique(data, categories, expected_data, ordered) without return types